JSP built-in objects

Js| Object

①out-javax.servlet.jsp.jspwriter
The Out object is used to output the results to the Web page.

Method:
1. void clear ();
Clears the contents of the output buffer, but does not output to the client.

2. void Clearbuffer ();
Clears the contents of the output buffer and outputs it to the client.

3. void Close ();
Closes the output stream and clears all content.

4. void Flush ();
The data inside the output buffer.

5. int getbuffersize ();
Gets the current buffer size in kilobytes.

6. int getremaining ();
Gets the amount of space that is not occupied in a buffer in kilobytes.

7. Boolean Isautoflush ();
Whether the buffer is automatically refreshed.

8. void newline ();
Output a newline character.

9. void Print (Boolean b);
   void print (char c);
   void Print (char[] s);
   void print (double d);
   void print (float f);
   void print (int i);
   void print (long L);
   void print (Object obj);
   void print (String s); The
   outputs the data of the specified type to the HTTP stream without wrapping.

void println (Boolean B);
void println (char c);
void println (char[] s);
void println (double D);
void println (float f);
void println (int i);
void println (long L);
void println (Object obj);
void println (String s);
Outputs the specified type of data to the HTTP stream and outputs a newline character.

Appendable append (char c);
Appendable Append (charsequence cxq, int start, int end);
Appendable Append (charsequence cxq);
Adds a character or an object that implements the Charsequence interface to the back of the output stream.

Members:
int default_buffer = 0-Default buffer size
int no_buffer = -1-writer is in buffered output state
int unbounded_buffer =-2-Limit buffer size

②request-javax.servlet.http.httpservletrequest
The Request object contains all the requested information, such as the source of the request, headers, cookies, and request-related parameter values.

Method:
1. Object getattribute (String name);
Returns the value of the property specified by name, which returns null if the property does not exist.

2. Enumeration Getattributenames ();
Returns a collection of all the property names for the request object.

3. String Getauthtype ();
Returns the name of the authentication method used to protect the servlet and returns NULL when unprotected.

4. String getcharacterencoding ();
Returns the character encoding method in the request, which can be set in the response object.

5. int getcontentlength ();
Returns the length of the requested body, not 1 when the length is not determined. Can be set in response.

6. String getContentType ();
Returns the type of content defined in response.

7. String Getcontentpath ();
Returns the path of the request.

8. cookie[] GetCookies ();
Returns an array of all cookies for the client.

9. Enumeration Getheadernames ();
Returns a collection of the names of all HTTP headers.

Enumeration Getheaders (String name);
Returns a collection of all values for the specified HTTP header.

A. String GetHeader (string name);
Returns information about the HTTP header for the specified name.

Long Getdateheader (String name);
Returns information for the HTTP header of the data type of the specified name.

Getintheader Int (String name);
Returns information for the HTTP header of the type int of the specified name.

ServletInputStream getInputStream ();
Returns the input stream for the request.

Locale GetLocale ();
Returns the locale object for the current page, which can be set in response.

Enumeration Getlocales ();
Returns a collection of all the locale objects in the request.

String Getlocalname ();
Gets the server-side host name of the response request.

A. String getlocaladdr ();
Gets the server-side address of the response request.

Getlocalport Int ();
Get the server-side port that responds to the request

String GetMethod ();
Gets the method (get, POST) that the client sends the request to the server side.

String GetParameter (string name);
Gets the parameter values that the client sends to the server side.

Map Getparametermap ();
This method returns a Map object that contains all the parameters in the request.

Enumeration Getparameternames ();
Returns a collection of all the parameters in the request.

String[] Getparametervalues (String name);
Gets all the values for the specified parameter in the request.

String getquerystring ();
Returns the string of arguments passed by the Get method, which does not break out individual parameters.

A. String getpathinfo ();
Remove additional information between Servletpath and QueryString in the request.

A. String getpathtranslated ();
Returns the actual path of the path information obtained using the GetPathInfo () method.

String Getprotocol ();
Returns the protocol used by the request. It can be HTTP1.1 or HTTP1.0.

BufferedReader Getreader ();
Returns the reader object for the requested input stream, which can only be invoked on one page for a getInputStream () method.

String getremoteaddr ();
Gets the client IP address that issued the request.

String Getremotehost ();
Gets the client host name that issued the request

String Getremoteuser ();
Returns a client-authenticated user name that returns null without validation.

Getremoteport Int ();
Returns the client host port on which the request was made.

Getrealpath string (string path);
Returns the physical path of the given virtual path.

RequestDispatcher getrequestdispatcher (String path);
Generates a resource by the given path to process the adapter object.

A. String Getrequestedsessionid ();
Returns the identity of the requested session.

RequestUri String ();
Returns the client address that issued the request, but does not include the requested parameter string.

StringBuffer Getrequesturi ();
Returns the server-side address of the response request

Getscheme String ();
Gets the protocol name, which defaults to the HTTP protocol.

getServerName String ();
Returns the name of the server that responded to the request.

A. String Getservletpath ();
Gets the file path of the script file requested by the client.

Getserverport Int ();
Gets the server-side host port number in response to the request.

removeattribute void (String name);
Deletes the property of the specified name in the list of properties.

void SetAttribute (String name, Object value);
Adds/deletes the specified property to the list of properties.

setcharacterencoding void (String name);
Sets the character encoding format of the request.

HttpSession getsession ();
HttpSession getsession (Boolean create);
Gets the session, if Create is true, and creates one without a session.

Boolean Isrequestedsessionidfromcookie ();
Check that the requested session ID is passed through a cookie.

Boolean Isrequestedsessionidfromurl ();
Checks whether the requested session ID is passed in by URL.

Boolean isrequestedsessionidvalid ();
Check that the requested session ID is still valid.

Boolean issecure ();
Check whether the request uses a secure link, if HTTPS, and so on.

A Boolean isuserinrole (String role);
Check to see if the user who has passed the validation is in the role specified by roles.

Principal Getuserprincipal ();
Returns a Java.security.Principal object that contains the user login name.

Members:
String Basic_Auth = "BASIC"-
String Client_cert_auth = "Client_cert"-
String Digest_auth = "DIGEST"-
String Form_auth = "FORM"-

③response-javax.servlet.http.httpservletresponse
The response object mainly passes the results of the JSP container processing back to the client.

Method:
1. Void Addcookie (cookie cookie);
Add a Cookie object to save the client information.

2. void Adddateheader (String name, Long value);
Adds HTTP header information for a date type, overwriting HTTP header information with the same name.

3. void AddHeader (string name, string value);
Add an HTTP header that overwrites the old HTTP header with the same name.

4. void Addintheader (String name, int value);
Adds an integer HTTP header that overwrites an old HTTP header with the same name.

5. Boolean Containsheader (String name);
Determines whether the specified HTTP header exists.

6. String encoderedirecturl (string url);
Encodes the URL used by the Sendredirect () method.

7. String encodeurl (string url);
Encodes the URL to return the URL that contains the session ID.

8. void Flushbuffer ();
Forces the contents of the current buffer to be sent to the client.

9. int getbuffersize ();
Gets the size of the buffer in kilobytes.

String getcharacterencoding ();
Gets the character encoding format of the response.

A. String getcontenttype ();
Gets the type of the response.

Locale GetLocale ();
Gets the locale object for the response.

Servletoutputstream Getoutputstream ();
Returns the output stream object for the client.

PrintWriter getwriter ();
Gets the writer object that corresponds to the output stream.

Boolean iscommitted ();
Determine if the server side has output data to the client.

void Reset ();
Clears all content in the buffer.

void Resetbuffer ();
All content in buffer, but preserves HTTP headers and state information.

void Senderror (int xc, String msg);
void Senderror (int xc);
Send errors, including status codes and error messages.

(a) void Sendredirect (String locationg);
Send the response to another location for processing.

void setbuffersize (int size);
Sets the size of the buffer in kilobytes.

void Setcharacterencoding (String charset);
Sets the character encoding format used by the response.

void setcontentlength (int length);
Sets the body length of the response.

setContentType void (String type);
Sets the type of response.

void Setdateheader (String name, Long value);
Sets the value of the HTTP header for the data type of the specified name.

SetHeader void (string name, string value);
Sets the value of the HTTP header for the specified name.

Setintheader void (String name, int value);
Sets the value of the HTTP header for the type int of the specified name.

(a) void setstatus (int xc);
Sets the response status code, and the new value overrides the current value.

member (HTTP status code):


int sc_continue = int Sc_switching_protocols = 101


int sc_ok = int sc_non_authoritative_information = 203


int sc_accepted = sc_created int = 201


int sc_no_content = 204 int sc_reset_content = 205


int sc_partial_content = 206 int sc_multiple_choices = 300


int sc_moved_permanently = sc_moved_temporarily = 302


int sc_found = 302 int sc_see_other = 303


int sc_not_modified = 304 int sc_use_proxy = 305


int sc_temporary_redirect = 307 int sc_bad_request = 400


int sc_unauthorized = 401 int sc_payment_required = 402


int sc_forbidden = 403 int sc_not_found = 404


int sc_method_not_allowed = 405 int sc_not_acceptable = 406


int sc_proxy_authentication_required = 407 int sc_request_timeout = 408


int sc_conflict = 409 int sc_gone = 410


int sc_length_required = 411 int sc_precondition_failed = 412


int sc_request_entity_too_large = 413 int sc_request_uri_too_long = 414


int sc_unsupported_media_type = 415 int sc_requested_range_not_satisfiable = 416


int sc_expectation_failed = 417 int sc_internal_server_error = 500


int sc_not_implemented = 501 int sc_bad_gateway = 502


int sc_service_unavailable = 503 int sc_gateway_timeout = 504


int sc_http_version_not_supported = 505

④session-javax.servlet.http.httpsession
The Session object represents the current conversation state of individual users and is used to identify each user.

Method:
1. Object getattribute (String name);
Gets the value of the session property associated with the specified name.

2. Enumeration Getattributenames ();
Gets a collection of all the attributes within the session.

3. Long GetCreationTime ();
Returns the creation time of the session, with a minimum unit of 1 per thousand seconds.

4. String getId ();
Gets the session ID.

5. Long Getlastaccessedtime ();
Returns the last access time for the client associated with the current session, measured in milliseconds from 1970-01-01.

6. int getmaxinactiveinterval (int interval);
Returns the total time, in seconds, that represents the active time of the session (the session inactivity time). -1 is never expired.

7. ServletContext Getservletcontext ();
Returns an instance of the ServletContext object corresponding to the JSP page.

8. Httpsessioncontext Getsessioncontext ();

9. Object GetValue (String name);
Gets the value of the session variable for the specified name and is not recommended for use.

String[] GetValueNames ();
Gets a collection of the names of all session variables and is not recommended for use.

A. void invalidate ();
Destroy this session object.

Boolean isnew ();
Determines whether a session is generated by the server, but is not used by the client.

Pubvalue void (String name, Object value);
Add a session variable that is not recommended for use.

removevalue void (String name);
Removing the value of a session variable is not recommended.

void setattribute (string name, string value);
Sets the value of the session property for the specified name.

void setmaxinactiveinterval (int interval);
Sets the duration of the session.

void RemoveAttribute (String name);
Removes the session property of the specified name.

⑤pagecontext-javax.servlet.jsp.pagecontext
The PageContext object stores information related to this JSP page, such as attributes, built-in objects, and so on.

Method:
1. void setattribute (String name, Object value, int scope);
void SetAttribute (String name, Object value);
Sets the property within the specified shared scope.

2. Object getattribute (String name, int scope);
Object getattribute (String name);
Gets the value of the property within the specified shared range named by name.

3. Object Findattribute (String name);
Searches for named properties by page, request, session, and application sharing scope.

4. void RemoveAttribute (String name, int scope);
void RemoveAttribute (String name);
Removes the property for the specified name and shared scope.

5. Void forward (String URL);
Navigates the page to the specified URL.

6. Enumeration Getattributenamesscope (int scope);
Gets a collection of all the property names within the specified shared scope.

7. int Getattributescope (String name);
Gets the shared scope of the specified property.

8. ErrorData geterrordate ();
Gets the ErrorData object for the page.

9. Exception getexception ();
Gets the exception object for the page.

ExpressionEvaluator Getexpressionevaluator ();
Gets the ExpressionEvaluator object for the page.

JspWriter getout ();
Gets the Out object of the page.

Object GetPage ();
Gets the page object for the sheet.

ServletRequest getrequest ();
Gets the request object for the page.

Servletresponse GetResponse ();
Gets the response object for the page.

ServletConfig GetConfig ();
Gets the config object for the page.

ServletContext Getservletcontext ();
Gets the ServletContext object for the page.

HttpSession getsession ();
Gets the session object for the page.

Variableresolver Getvariableresolver ();
Gets the Variableresolver object for the page.

void include (String URL, boolean flush);
void include (String URL);
Contains additional resources and specifies whether to refresh automatically.

void release ();
Resets the PageContext internal state, releasing all internal references.

void Initialize (servlet servlet, servletrequest request, servletresponse response,
String Errorpageurl, Boolean needsession, int buffersize, Boolean autoflush);
Initializes an uninitialized PageContext object.

Bodycontext Pushbody ();
Bodycontext pushbody (Writer Writer);
Saves the current out object and updates the Out object in page range in PageContext.

Jspwrite Popbody ();
Remove the Out object saved by the Pushbody () method.

void Handlepageexception (Exception e);
void Handlepageexception (Thrwoable t);

Members:
int page_scope = 1-page Share range
int request_scope = 2-Request Shared scope
int session_scope = 3-session sharing scope
int application_scope = 4-Application Sharing scope
String PAGE = "Javax.servlet.jsp.jspPage"
String PageContext = "Javax.servlet.jsp.jspPageContext"
String REQUEST = "Javax.servlet.jsp.jspRequest"
String RESPONSE = "Javax.servlet.jsp.jspResponse"
String CONFIG = "Javax.servlet.jsp.jspConfig"
String session = "Javax.servlet.jsp.jspSession"
String out = "Javax.servlet.jsp.jspOut"
String application = "Javax.servlet.jsp.jspApplication"
String EXCEPTION = "Javax.servlet.jsp.jspException"

⑥application-javax.servlet.servletcontext
The main function of application is to obtain or change the servlet settings.

Method:
1. Object getattribute (String name);
Returns the Application property specified by name.

2. Enumeration GetAttributes ();
Returns all the application properties.

3. ServletContext getcontext (String uripath);
Gets the ServletContext object for the current application.

4. String Getinitparameter (string name);
Returns the initial value of the application property specified by name.

5. Enumeration Getinitparameters ();
Returns a collection of the initial values for all application properties.

6. int getmajorversion ();
Returns the version number of the Servlet API supported by the servlet container.

7. String GetMimeType (string file);
Returns the type of the specified file, and the unknown type returns NULL. Generally "text/html" and "Image/gif".

8. int getminorversion ();
Returns the version number of the Servlet API supported by the servlet container.

9. String Getrealpath (string path);
Returns the physical path corresponding to the given virtual path.

RequestDispatcher getnameddispatcher (String name);
Returns an instance of a RequestDispatcher object for the Servlet object of the specified name.

RequestDispatcher getrequestdispatcher (String path);
Returns an instance of a RequestDispatcher object.

A. URL getresource (String path);
Returns an instance of the URL object for the specified resource path, with the argument starting with "/".

InputStream getResourceAsStream (String path);
Returns an instance of the InputStream object for the resource at the location specified by path.

Set getresourcepaths (String path);
Returns a collection of all resource paths stored in Web-app.

String Getserverinfo ();
Gets the application server version information.

Servlet Getservlet (String name);
Retrieves the servlet of the specified name in ServletContext.

Enumeration Getservlets ();
Returns a collection of all the servlet in ServletContext.

A. String getservletcontextname ();
Returns the name of this Web application.

Enumeration Getservletcontextnames ();
Returns a collection of the names of all the servlet in ServletContext.

void log (Exception ex, String msg);
void log (String msg, Throwable t);
void log (String msg);
Writes the specified information to the servlet log file.

void RemoveAttribute (String name);
Removes the application property of the specified name.

void SetAttribute (String name, Object value);
Sets the value of the specified application property.

⑦config-javax.servlet.servletconfig
Config object is used to store the initial data structure of the servlet.

Method:
1. String Getinitparameter (string name);
Returns the value of the push parameter named name.

2. Enumeration Getinitparameters ();
Returns a collection of the names of all the prompting parameters for this JSP.

3. ServletContext GetContext ();
Returns the servlet context of the performer.

4. String getservletname ();
Returns the name of the servlet.

⑧exception-java.lang.throwable
Error object, you can use the exception object on this page only if you specify Iserrorpage= "true" in the page instruction of the JSP page.

Method:
1. Throwable fillinstacktrace ();
Logs the current stack information to the exception object.

2. String getlocalizedmessage ();
Gets the local language family error message.

3. String GetMessage ()
Get the error message.

4. stacktrackelement[] Getstacktrace ();
Returns the call stack track information recorded in the object.

5. Throwable initcause (throwable cause);
Nesting another exception object into the current exception object.

6. Throwable getcause ();
Removes the exception that is nested in the current exception object.

7. void Printstacktrace ();
void Printstacktrace (PrintStream s);
void Printstacktrace (PrintWriter s);
Print out Throwable and its call stack trace information.

8. Void Setstacktrace (stacktraceelement[] stacktrace)
Sets the call stack trace information for an object.

⑨page-javax.servlet.jsp.httpjsppage
The Page object represents the JSP object itself, or represents a compiled Servlet object.
You can use the ((javax.servlet.jsp.HttpJspPage) page) to fetch its methods and properties.